Boresighting is generally employed to align various systems to a frame of reference of a vehicle (e.g., an aircraft, a tank, a ship). Such systems may be armament systems (e.g., guns, missiles mounting devices), guidance systems such as radar or tracking systems such as operator head tracking systems. Boresighting such systems to the frame of reference of the vehicle is required for such systems to operate properly. More generally, boresighting relates to determining the relative orientation between two different locations.
U.S. Pat. No. 5,619,323 to Hamilton et al, entitled “Gyroscopic System for Boresighting Equipment by Transferring a Frame of Referenced” directs to system and a method for aligning the frame of reference of various equipment, such as sensors, guns camera and antennae located on an aircraft, with the reference axis of the aircraft. The system directed to by Hamilton et al includes a first stationary inertial sensor that is boresighted with respect to a reference line of the aircraft. This first inertial sensor includes a first gyroscopic combination for generating a first output indicating a frame of reference (i.e., either 2D or 3D) based on the reference line and a docking station. The docking station facilitates alignment of a second portable inertial sensor which also includes a gyroscopic combination for generating a second output indicating the frame of reference thereof.
One of the methods directed to by Hamilton et al includes boresighting the first stationary inertial sensor with respect to the reference line of the aircraft and positioning the second portable inertial sensor on the docking station of the first inertial sensor for aligning the two inertial sensors. Then the outputs from respective first inertial sensor and from the second inertial sensor are processed to determine the difference between the respective frames of reference thereof. The second portable inertial sensor is then aligned with respect to a device to be boresighted. The outputs respective of the first inertial sensor and the second inertial sensor are then processed to determine a third frame of reference of the second portable inertial sensor relative to the first stationary inertial sensor. The difference between the first, second and third frames of reference is calculated to align the device with respect to the reference line.
To increase the accuracy of the boresighting the first inertial unit may be provided with a mirror having first and second nonplanar surfaces and the second inertial unit is provided with a gimbal and gimbal drive system, a laser beam generator for projecting a laser beam and a collimator for indicating an angle between two beams. With such a system, the method includes the steps of positioning a laser beam from the beam generator of the second portable inertial sensor to the mirror mounted on the first stationary inertial sensor, form which the beam is reflected. Then the angle between the projected beam and the reflected beam is measured with the collimator of the second inertial unit. The first, second and third outputs from the respective first inertial unit, second inertial unit and collimator are processed to determine a first frame of reference of the second portable inertial sensor relative to the first stationary inertial sensor. The portable second inertial sensor is then aligned with respect to the device to be boresighted. The first, second and third outputs from the respective first inertial unit, second inertial unit and collimator are again processed to determine a second frame of reference of the second portable inertial sensor relative to the first stationary inertial sensor. Then, difference between the first frame of reference and the second frame of reference is calculated to determine the alignment of the device with respect to the reference line.
European patent application publication EP 2 602 581 to Jones et al, entitled “Field Interchangable Boresight Mounting System and Calibration Method” directs to a system for calibrating a tray on which a boresighting device is to be mounted. The system directed to by Jones et al includes amounting system, which further includes a frame alignment measurement sensor and a frame movement sensor. The alignment measurement sensor is affixed to the device to be boresighted and optionally affixed to an adapter. The frame movement sensor is affixed directly to mounting tray. The movement sensor measures the attitude changes of the mounting tray. According to Jones at el, the measurement sensor is placed in a first position and orientation and the angular position of the tray is measured. Then the measurement sensor is moved to a second position and orientation and the angular position of the tray is measured. The As long as the mounting tray remains in the same position, the static offset errors of the boresighting device and the adapter, as well as misalignment errors of the mounting tray, will be observed by the relative changes in pitch and roll, from the starting first position to the second position. The alignment measurement sensor is then moved back to the first position and the angle of the angular position of the tray is measured again. This repeated measurement enables the system directed to by Jones et al to determine whether a current position of the alignment measurement sensor is within repeatability bounds.
U.S. Patent Application Publication 2010/0332181 to Jones et al, entitled “System and Method for Determining Angular Differences on a Potentially Moving Object” directs to a boresight alignment system which includes two independent navigating inertial reference units (IRUs) mounted on a flight vehicle. A first IRU measures the angular difference between two points on an aircraft. The second IRU measures any angular changes that may take place on the aircraft. Thus the chassis of the aircraft may be in motion while the alignment procedure is being performed. Moreover, the aircraft can be located on a moving platform such as an aircraft carrier.
In operation, the system directed to by Jones et al records angular information relating to frame of reference of the alignment sensor and the movement sensor at a first boresight position at a first point in time. The alignment sensor is relocated to a second boresight position on the object at a second point in time. Then the frame of reference angular information of the alignment sensor and the movement sensor at this second position is recorded at a second point in time. The system directed to by Jones et al employs these four sets of data to determine the alignment of the first boresight position to the second boresight position. Moreover, the system directed to by Jones et al selectively measure these two sets of data at a point in time where motion is at or below a prescribed limit based on a selected measurement accuracy level. The differences between the first position and the second position is then determine. The movement sensor (the second IRU) is attached to the object and configured to detect any angular movement of the object between recording of the first, the second, and any subsequent measurements. For example, any rotation of the object is detected by the movement sensor and is used during boresight alignments or subsequent boresight realignments to correct the difference measurement for the amount of angular movement that has occurred on the object.